Time response analysis of ZnSe-based Schottky barrier photodetectors

We report on the characterization of ZnSe- and ZnMgBeSe-based Schottky barr ier photodetectors grown on semi-insulating GaAs(001) by molecular-beam epi taxy. The spectral response of the devices shows a very sharp cutoff at var iable wavelength, determined by the alloy composition, with a large stop-ba nd rejection. Short-wavelength responsivities of 0.10 A/W and detectivities as high as 1.4x10(12) cm Hz(1/2) W-1 at -3.5 V bias have been achieved. Th eir time response behavior has been analyzed in detail. When light is switc hed off, the devices show photocurrent decays in the microsecond range, con sisting of two exponential components with very different time constants. T he slower component becomes dominant for high load and reverse bias. This b ehavior is related to the strong frequency dependence of the device capacit ance. (C) 2000 American Institute of Physics. [S0003-6951(00)03643-3].